Question

The height of a ball in meters is modeled by f(x) = -5x^2 + 40x where x is the time in seconds after the ball is hit. How long is the ball in the air?

Answer 1

The ball is in the air for 8 seconds.

Explanation:

To know how long the ball is in the air we need to know when the ball hit the ground; to figure this out we need to factor this equation to know the x-intercepts.

-5x^2 + 40x = 0

-5x ( x - 8 ) = 0

x - 8 = 0

x = 8 ( when it lands)